This invention is related to a method of making a modified silica filler in which silica is contacted with a blend or mixture of a diorganodihalosilane and a monoorganotrihalosilane in a weight ratio of 1:0.1 to 1:2, respectively.
This is an improvement in methods of modifying silica fillers, as described in for example, U.S. Pat. No. 6,384,125 (May 7, 2002), which is assigned to the same assignee as the present invention. While the ""125 patent refers generally to the use of some similar organometallic compounds and mixtures thereof as the present invention, and their use as hydrophobing agents for silica, it does not describe any particular mixture or blend of chlorosilane compounds as being any more effective than any other blend, nor does the ""125 patent identify the existence of any particular ratio of silane compounds as being necessary to achieve a new and unexpected results, i.e., an ability to deposit more siloxane on silica, vis a viz, improved hydrophobicity.
The invention is directed to a method of making modified silica fillers in which silica is contacted with a blend or mixture of organosilicon compounds. In particular, it is directed to an improvement in treating silica with blends or mixtures of diorganodihalosilanes and monoorganotrihalosilanes, in weight ratios of 1:0.1 to 1:2, respectively.
Preferably, the weight ratio is 1:0.3 to 1:1, and most preferably the weight ratio is 1:0.5. Similarly, the blend or mixture is preferably a dialkyldichlorosilane and a monoalkyltrichlorosilane, and most preferably dimethyldichlorosilane and methyltrichlorosilane. In some additional embodiments, the blend or mixture may also comprise compositions containing (i) dimethyldichlorosilane, (ii) n-propyltrichlorosilane, phenyltrichlorosilane, or cyanopropyltrichlorosilane, and (iii) mercaptopropyltriethoxysilane.